Stencil duplicating inks



United States Patent lce STENCIL DUPLICATING INKS Thomas Seal Chambers, Chicago, and Robert Thompson Florence, Park Ridge, 111., assignors to A. B. Dick Company, Niles, 11]., a corporation of Iliinois No Drawing. Application March 27, 1952, Serial No. 278,946

6 Claims. (Cl. 106-25) This invention relates to water base stencil duplicating inks adapted for use with stencil duplicating machines or for use in other stencilling operations where ink is transferred through stencil openings to an impression medium. This application is a continuation-in-part of our copending application Ser. No. 93,414, filed May 14, 1949, and now abandoned.

In a stencil duplicating machine of the rotary type or the like, ink is supplied in continuous fashion to an ink pad or other like reservoir or distributing medium. After uniform distribution therein, the ink is transferred through the openings of a stencil to the impression medium, chiefly in response to forces developed at the point. of contact between a rotating cylinder and the impression roller. For the most part, drying of the applied ink occurs by absorption of the vehicle or carrier into a portion of the impression medium or into the interstices between the fibers of which the impression medinmis formed.

The characteristics desirable in a stencil duplicating ink are manifold and in many respects non-analogous to ink compositions commonly used for printing or for writing. For example, in order to function properly in the duplicating machine, the ink should have sufficient body to minimize leakage from the cylinder and the ink pad and to prevent flooding of the stencil. On the other hand, in order to produce uniform and good copy, the ink should have suflicient flow to effect satisfactory transmission through the stencil to the impression medium and to enable uniform and rapid distribution of the ink through the ink pad. The ink should be sufiiciently slow drying in the machine to minimize premature hardening on the ink pad or undesirable clogging of the stencil openings. At the same time, the ink should be quick drying when applied to the impression medium, otherwise it is necessary to resort to special devices or other costly practices in order to handle copy within a reasonable time and to eliminate setoif. The ink should dry without feathering, without forming an oily or colored letter outline, referred to by the industry as halo, and it should not be subject to show-through, which may be defined as visibility from the opposite side of the impression medium. The ink should also be stable and non-corrosive to the machine parts with which it might come in contact. Upon drying, it should be resistant tomoisture, the common solvents and other substances with which the copy might come in contact as an incidence to normal use.

Many of these characteristics are wholly lacking in stencil duplicating inks that have heretofore been produced. Preparation of an acceptable stencil duplicating ink has, in the past, been limited because of the presence of large amounts of oil, deemed necessary to provide for flow of the desired character and to function simultaneously as the carrier for the coloring agent. The greater proportion of oils which have been used are selected of the non-drying type such as castor oil, palm oil, and cocoanut oil.

When such oils, which are non-drying in character, are

2,771,374 Patented Nov. 20, 1956 used in large amounts, they permit a highly objectionable degree of setoif and smear un'less special devices are used in the handling of the copy. The commonest device to cope with this problem is the costly and awkward practice of slip-sheeting, that is, the insertion of interlayer sheets between successive copies as they are duplicated. The problem may be alleviated, to a limited extent, by using as the .impression medium highly absorbent paper stock which rapidly distributes the vehicle, but the use of such absorbent medium makes it practically impossible to obtain sharply defined copy because of feathering of the ink.

The high oil content is directly responsible for the presence of objectionable letter outlines or halo in copy prepared with oil-base inks. Stencil duplication with oilbase ink is burdened further by the fact that its use is limited to impression media of a highly absorbent nature and cannot be used successfully with hard or highly filled paper such as card, ledger, bond, or enamel stock.

Oil-base emulsion inks constituted with less oil have been formulated to relieve some of the objectionable features of the non-emulsion inks, but many of the limitations inherent in the oil still remain. Emulsion inks which have heretofore been produced present other operating problems because they are characterized by lower stability and separation often occurs at some stage in its use prior to transmission through the stencil, whereby the ink pad or the stencil, or both, may become clogged to prevent uniform ink distribution and complicate the production of good copy. In addition, the inner phase of the ink emulsion frequently contains sulfonated glycerides, which are corrosive to the machine part or other elements with which the ink might be associated.

It is an object of this invention to produce a stencil duplicating ink which contains a desired balance in characteristics of the type previously described.

Another object is to produce a stencil duplicating ink that is substantially free of oil and is thereby not limited to the restrictions imposed by the use of oily substances.

A further object is to produce a stencil duplicating ink having fiow of the desired character in proper balance to operate successfully in stencil duplicating machines and other processes in the production of copy of good quality.

A still further object is to produce an oil-free stencil duplicating ink which has the desired balance of slow drying while in the stencil duplicating machine and quick drying upon transmission to the impression medium.

A still further object is to produce a stencil duplicating ink which may be used for the production of copy on hard, filled, or highly finished impression media without slip-sheeting or the use of other costly and undesirable devices.

Another object is to produce a stencil duplicating ink which is quick drying so as to permit handling of the copy almost immediately after duplication without setoff or smear, and which, upon drying, becomes substantially impervious to moisture, many hydrocarbons and solvents withwhich the copy might come in contact.

A further object is to produce a stencil duplicating ink which is not subject to the objectionable features of ink compositions which have heretofore been produced and which is capable of meeting substantially all of the characteristics desired in a good stencil duplicating ink.

A still further object is to produce a low-viscosity stencil l duplicating ink having flow of the desired character and which is substantially non-corrosive, non-inflammable, stable, safe and easy to manufacture and use.

A very important object of this invention is to formulate a stencil duplicating ink without the use of oil. This we have succeeded in accomplishing by the production of a water-'basesten'cil duplicating ink having characteristics that surpass ink compositions which have heretofore been developed.

The term water base may be used to define inks prepared in accordance with our invention because water is present as the major diluent and carrier and is used to dissolve the bodying agents which impart flow of the desired character. In the practice of this invention, the water content of the ink composition may be as high as 75 to 85% by weight of the composition.

Water-base stencil duplicating inks embodying features of our invention are characterized by having a measurable viscosity which is much lower than the viscosity of oil-base inks or oil-emulsion inks operable under corresponding conditions. Viscosity can be used as a measure for certain flow characteristics, yet we find it impractical presently to define the desired flow characteristics rigidly and exclusively in the terms of viscosity. When measured by a Stormer Viscosimeter using a standard cup with a thermometer well and with a center bafile and while operating under a ZOO-gram load at 20 C., water-base inks embodying features of this invention provide a reading between 35 to 150 seconds. Suitable oil-base inks have a reading between 800 and 1000 seconds, and many oil-emulsion inks have a reading between 650 and 800 seconds. The lower viscosity permissible with Waterbase inks of the type produced by this invention. favors more rapid and uniform distribution of the ink throughout the ink pad and greater ease of transmission and operation in the duplicating process.

Body or fiow of the desired character in the stencil duplicating ink composition is achieved by solution therein of a water-soluble carbohydrate or polysaccharides including starch, sugars, dextrin, glycogens, pectins, saponins and gums such as gum arabic, karaya gum, gum tragacanth, and marine polysaccharides such as agar, carrageen, alginic acid, and alginates, such as sodium alginate and the like.

In practice, the desired bodying and flow characteristics in the ink composition may be secured by the use of about 1 to 30% by weight the starches, glycogens, and pectins, considerably higher, such as up to 80% sugars and dextrins, and the use of about 1 to 10% gum tragacanth or 5 to 30% gum arabic. Considerably lesser amounts of the marine polysaccharides are necessary to impart the desired flow characteristics. For example, alginates in amounts ranging from 0.5 to 5% by weight are sufficient, and the desirable results may be secured by corresponding amounts of agar carrageen and the like. T he viscosity range is not to be taken as a strict limitation for defining the concentration of the bodying agent to be used therein, because the fiow requirements for the ink composition changes in accordance with modifications in duplicating machines and in the practices of their use. Therefore, it will be understood that changes in amounts of such bodying agents may be made in accordance therewith without departing from the spirit of the invention.

As coloring agent, dyes or pigments, soluble or dispersible in aqueous medium may be used. Representative of the class of dyes having the desired solubility characteristics are the nigrosine dyes, triphenylmethane dyes, rhodamine dyes, thioflavine dyes, auramine dyes, quinonimide dyes, xanthane dyes, sulphonated triphenylmethane dyes, and nitro dyes. These include acid dyes such as the mono-, di-, and tri-sodium sulphonates of the nitro, azo, pyrazoline, quinoline, azine, xanthane, and anthraquinone groups. Suitable pigments include lamp black, zinc oxide, titanium oxides, malachite green, iron blue, cadmium yellow, and the like. When pigments are used, they are usually dispersed as the discontinuous phase in suitable carriers such as water, solutions of resin, and the like.

The amount of dye in any formulation depends upon the characteristics of the coloring material. Some dyes, even when used in small quantities, are capable of imparting suflicient color to lend legibility to the copy.

With others, it is necessary to use higher concentrations of dye to secure the desired effect. The lower limit of dye concentration is determined by its tinctorial strength, which may vary widely from compound to compound. The upper limit is often influenced by solubility factors or by the effect of the dye on other ingredients of the ink composition. We have found that Water-soluble nigrosin dyes in amounts ranging from 3 to 7% by weight are suitable for water-base stencil duplicating inks. Other dyes may be used in corresponding ratio in accordance with their characteristics as pointed out above. When pigments are used, it is often desirable to use concentrations higher than 3% by weight, with the upper limit being in the range of about 15% by weight or more in some instances.

in order to increase the penetrability of the duplicating ink into the impression medium, and in order to improve the characteristics of the ink with respect to its distribution through the ink pad of the stencil, it is desirable to incorporate a wetting agent as an ingredient in the composition. A suitable wetting agent may be selected from well-known materials such as the dioctyl esters of sodium sulfosuccinates (Aerosols), quaternary ammonium salts in which one of the organic groups is a fatty acid of higher carbon length (Duponols), dibutylphenol sodium disulfonates (Areskelene), sulfonated ethers (Tensol), or the like. Less than 2%, but more than 0.2% by weight of wetting agent is ordinarily suflicient to impart the desired wetting characteristics, although more may be used, if desired.

Another important modification in stencil duplicating compositions embodying features of this invention comprises the addition of a humectant which operates to reduce the rate of evaporation of the diluent. More important, the humectant appears in some instances to be capable of modifying the apparent flow properties of the ink composition. Such modification is not necessarily measurable by viscosimeters operating at high shear, but exists in fact to the extent that leakage from the ink pad is greatly minimized and operation of the duplicating machine substantially simplified. Under high shear, such as the forces operating while the ink is being forced through the stencil during duplication, the modified flow properties are not apparent, and, therefore, the ink flows as a liquid apparently having little additional viscosity. Liquid polyhydric alcohols, such as ethylene glycol, diethylene glycol, glycerine, and polyglycols, appear to impart these characteristics. Use may also be made of alkylolamines such as diethanolamine, triethanolamine sulfamate, monoisopropanolamine sulfamate, and the like. In specific application, from 10 to 40 percent by weight of the polyhydric alcohols may be used as an ingredient of the ink composition. Some of the sugars which may be used as bodying agents may also supply some of the properties of a humectant and therefore enable the use of less thereof for equivalent properties.

In most instances, greater insolubilization of the carbohydrates and polysaccharides upon drying may be achieved by the use of an aldehyde latent while in aqueous solution, but which becomes reactive upon drying to insolubilize the bodying agents whereby they become more effective as a resistant adherent base for protecting the copy. Representative of such aldehydes are materials of the type glyoxal and pyruvic aldehyde. Glyoxal may be used in amounts of 5 percent by weight of the ink composition, or in amounts of about 5 to 20 percent by weight of the bodying substance. Larger amounts of pyruvic aldehyde may be required, such as up to 10 percent by weight of the ink composition to give corresponding results.

When insolubilization by reaction with a latent aldehyde is possible, it is preferred to use a polyhydric alcohol and the latent insolubilizing agent in combination in the same formulation. When so combined, the aldehyde is earn-374 able alsoto react with the'jpo'lyhydric alcohol as well as- V I Example-9 with the bodying material when constitutedwithhydroxyl or amino groups. The reaction 'is in the"'nature*of 21; Percentage Material condensation to form corresponding acetals',1hemiacetals* and P P 5.0". Nigrosine I (water soluble dye).;

Without limiting our invention to any particular com: e Wettmg agent Water 8011mm):v

. g n H 1.5 Glyoxal (30% solutionmwater). position, the following examples-will serveto illustrate 1o.o Ethylene glycol. suitable stencil duplicating inks 'embodying 'features' of" CleaPF 3 Starch In our invention:

Example 1 10 Example 10 Percentage Material Percentage Material Nigrosine J OolorIndex #865'(water soluble dye). Nigrosine I (water solnble dye). Gum arabic; 2.0 Dloctyl ester of sodium sulfosuccinate- Ethylene glycol. (50% solution). Water. 1.5 Glyoxal (30% S0l11tl011). 79.1; Mixed mono-, di-', and polysaccharides (Sweetose-A. E. Staley- 00.). E l 2 12.4 Water.

. Exam le 11 Percentage Material P V Nigrosinesl (water soluble dye). Percentage Material Guru are re.

Water.

Aquablak 1n aqueous dispersion. gl'lettinlg'ggit. l t YOXE SO I1 1011 Example 3 Ethylene glybol.

Tri-isopropanolamine salt oi alginic acid (7.2% solution in water) Percentage Material 5.0 Aquablak in aqueous;'dispersion (40% dispersion. of Example 12 carbon black in water). igIliIIIIIIIIIIIIII it??? Percentage Material Q 5. Ni'grosine I (water soluble dye). Example 4 "'1. Wetting agent.

1. Glyoxal (30% solution). a 1 Material y ene g yco Percentage 42 Water.

. Nigrosine I (water soluble dye). g i gr ose. Example 13 Percentage Material Example 5 liligrosilngg (weztter solublei dye). eroso we mg agen Percentage Materlal alyoxal solution).

. Ethylene glycol. Nigrosine J (water soluble dye). Alkylene glycol algmate. Gum tragacanth. Water. Water.

Example 14 Example 6 Percentage Material Percentage Material Nigrosine I (water soluble dye). Aerosol OT (wetting agent). Sodium alginate.

Water.

Material Aquablak in aqueous dispersion. Wetting agent.

#25 Dextrin, in water solution.

Water.

Example 8 Percentage Material Nigrosinc I (water soluble dye). Wetting agent (sodium suliosuccinate). Sodium alginate.

Water.

Aquablak, water dispersion. Wetting agent.

- Sodium alginate.

Water.

The materials in the above examples may be combined in any desirable order since they are generally miscible one with the other but it is preferred first to compound a viscous solution of the high molecular weight solution of bodying agent and water and then incorporate the other ingredients therein. When a pigment dispersion is employed, it may be incorporated into the formulation with suflicient stirring to distribute the dispersed pigment particles uniformly throughout the ink composition.

By the use of these new and improved stencil duplicating inks, drying has been found to take place at a speed which is beyond that heretofore contemplated for stencil duplicating inks of the oil base type thus making it possible to handle copy almost immediately. It is possible to eliminate set-off without the costly and cumbersome technique of slip-sheeting.

It has also been found possible .to produce copy on hard stock and highly finished impression medium while still being able to handle the work substantially immediately after duplication. The inks produced by this invention have been found to dry rapidly on bond, ledger, card or enamel stock, impression media which have heretofore not been suitable for general use with stencil duplicating machines.

The materials present in stencil duplicating ink compositions of the type described are incapable of producing an undesirable show-through or halo because the possible ingredients such as Water or other diluent are substantially completely eliminated from the impression medium upon drying and are not resident as are the oils of duplicating inks which have heretofore been produced.

It will be evident that a number of other important advantages are derived from the use of water base stencil duplicating inks of the type produced herein. These include the elimination of possible separation of the ingredients of the ink composition either in use or prior to use because of instabilities which might ordinarily have developed; simplification in the processes of cleaning a machine and stencil as by the use of a simple water rinse because the ink composition before drying remains readily soluble in water and any of the common solvents; self-sealing characteristics derived from the use of the polyhydric alcohol or the carbohydrate bodying agent alone or in combination; viscosity and flow properties so related to rate of shear that inadvertent flow in the ink cylinder is substantially eliminated without reducing the ability of the ink composition to pass through the stencil openings in normal duplicating operations; and simplicity in the manufacture of the ink compositions responsive chiefly to the use of water soluble elements as ingredients and the possible elimination of grinding or other means for incorporating the colors into the ink composition.

It will be understood that the basic substances may he prepared with a minimum amount of Water incorporated therein for marketing in concentrated form as a paste or without water incorporated therein for marketing in dry form for subsequent dilution at the station of use with aqueous medium to the desired viscosity. It will be further understood that miscible solvents, such as the lower alcohols may be substituted in part for water as the diluent in the ink composition. Numerous other modifications and substitutions may be made with respect to the materials and amounts and method of incorporation without departing from the spirit of the invention, especially as defined in the following claims.

We claim:

1.A stencil duplicating ink consisting essentially of more than 50 percent by Weight water as the principal diluent, from 3-15 percent by weight of a tinctorial agent,

from 05-30 percent by weight of a polysaccharide dissolved in the aqueous medium to body the ink composition and to provide an adherent base upon drying, and a liquid polyhydric alcohol present in an amount up to 40 percent by weight of the ink composition.

2. A stencil duplicating ink as claimed in claim 1 in which the polysaccharide comprises starch present in amounts ranging from 1-30 percent by weight.

3. A stencil duplicating ink as claimed in claim 1 in which the water soluble polysaccharide comprises a natural water soluble gum present in amounts ranging from 5-30 percent by weight.

4. A stencil duplicating ink as claimed in claim 1 in which the water soluble polysaccharide comprises a marine polysaccharide present in amounts ranging from 0.5-5 percent by weight.

5. A stencil duplicating ink consisting essentially of more than 50 percent by weight water as the principal diluent, from 3-15 percent by weight of a tinctorial agent, from 05-30 percent by weight of a polysaccharide dissolved in the aqueous medium to body the ink composition and to provide an adherent base upon drying, a liquid polyhydric alcohol present in an amount up to 40 percent by weight, 0.2-2 percent by weight of a wetting agent, and an aldehyde selected from the group consisting of glyoxal and pyruvic aldehyde present in amounts ranging from 5-20 percent by weight of the bodying agent.

6. A water base stencil duplicating ink consisting essentially of more than 50 percent by weight of water as the principal diluent, from 3-15 percent by weight of a tinctorial agent, from 0.5-30 percent by weight of a polysaccharide dissolved in the aqueous medium to body the ink composition and to provide an adherent base upon drying, a liquid polyhydric alcohol present in an amount up to 40 percent by Weight, and an aldehyde selected from the group consisting of glyoxal and pyruvic aldehyde present in an amount ranging from 5-20 percent by weight of the bodying agent.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A STENCIL DUPLICATING INK CONSISTING ESSENTIALLY OF MORE THAN 50 PERCENT BY WEIGHT WATER AS THE PRINCIPAL DILUENT, FROM 3-15 PERCENT BY WEIGHT OF A TINCTORIAL AGENT, FROM 0.5-30 PERCENT BY WEIGHT OF A POLYSACCHARIDE DISSOLVED IN THE AQUEOUS MEDIUM TO BODY THE INK COMPOSITION AND TO PROVIDE AN ADHERENT BASE UPON DRYING, AND A LIQUID POLYHYDRIC ALCOHOL PRESENT IN AN AMOUNT UP TO 40 PERCENT BY WEIGHT OF THE INK COMPOSITION. 